Characterization of focal liver lesions with contrast-enhanced ultrasound

Contrast-Enhanced Ultrasound of Focal Liver Lesions

OBJECTIVE

The purpose of this article is to discuss the use of contrast-enhanced ultra-sound (CEUS) in focal liver lesions.

CONCLUSION

Focal liver lesions are usually detected incidentally during abdominal ultrasound. The injection of microbubble ultrasound contrast agents improves the characterization of focal liver lesions that are indeterminate on conventional ultrasound. The use of CEUS is recommended in official guidelines and suggested as a second diagnostic step after ultrasound detection of indeterminate focal liver lesions to immediately establish the diagnosis, especially for benign liver lesions, such as hemangiomas, avoiding further and more expensive examinations.

Current consensus and guidelines of contrast enhanced ultrasound for the characterization of focal liver lesions

The application of ultrasound contrast agents (UCAs) is considered essential when evaluating focal liver lesions (FLLs) using ultrasonography (US). Microbubble UCAs are easy to use and robust; their use poses no risk of nephrotoxicity and requires no ionizing radiation. The unique features of contrast enhanced US (CEUS) are not only noninvasiveness but also real-time assessing of liver perfusion throughout the vascular phases. The later feature has led to dramatic improvement in the diagnostic accuracy of US for detection and characterization of FLLs as well as the guidance to therapeutic procedures and evaluation of response to treatment. This article describes the current consensus and guidelines for the use of UCAs for the FLLs that are commonly encountered in US. After a brief description of the bases of different CEUS techniques, contrast-enhancement patterns of different types of benign and malignant FLLs and other clinical applications are described and discussed on the basis of our experience and the literature data.

Evaluation of liver tumors using acoustic radiation force impulse elastography and correlation with histologic data

OBJECTIVES

Acoustic radiation force impulse (ARFI) technology represents an innovative method for the quantification of tissue elasticity. The aims of this study were to evaluate elasticity by ARFI in both liver tumors and background liver tissue and to compare ARFI measurements with histologic data in liver tumors and background liver.

METHODS

Seventy-nine tumors were prospectively studied: 43 benign and 36 malignant. Acoustic radiation force impulse measurements for each tumor type were expressed as mean ± standard deviation for both liver tumors and background liver; ARFI data were also correlated with histologic data.

RESULTS

For liver tumors, the mean stiffness values were 1.90 ± 0.86 m/s for hepatocellular adenoma (n = 9), 2.14 ± 0.49 m/s for hemangioma (n = 15), 3.14 ± 0.63 m/s for focal nodular hyperplasia (n = 19), 2.4 ± 1.01 m/s for hepatocellular carcinoma (n = 24), and 3.0 ± 1.36 m/s for metastasis (n = 12). Important variations were observed within each tumor type or within a single tumor. These variations could have been due to necrosis, hemorrhage, or colloid. There was no statistically significant difference between the benign and malignant groups. Regarding background liver, it was possible to observe pathologic abnormalities in histologic analyses or liver function tests to explain the ARFI data. The degree of fibrosis was not the only determinant of liver stiffness in background liver; other factors such as portal embolization, sinusoidal obstruction syndrome caused by chemotherapy, and cholestasis, also could have interfered.

CONCLUSIONS

Acoustic radiation force impulse elastography could not allow differentiation between benign and malignant tumors. This study provides a better understanding of the correlation between ARFI and histologic data for both tumors and background liver.

Liver metastases: Sulphur hexafluoride-enhanced ultrasonography for lesion detection: a systematic review

This is a systematic review to evaluate the accuracy of contrast-enhanced ultrasonography (CEUS) performed with "SonoVue" (sulphur hexafluoride) in the detection of hepatic metastases. The MEDLINE, EMBASE and COCHRANE Databases were searched, regardless of language, for relevant articles published before December 2009. Two reviewers independently assessed study eligibility using a standardized form and methodological quality using the quality assessment of diagnostic accuracy studies (QUADAS) Checklist. Sensitivity estimates were calculated on a per-patient and/or per-lesion basis. The search for published articles yielded 718 potentially relevant abstracts. Of these, 14 papers were eligible but only three articles fulfilled the inclusion criteria, which comprised a total of 450 patients (patient sample number: range 12 to 365; cancer prevalence: 14.8 to 71.2%). Estimated per-patient sensitivity ranged from 79-100%. Although the quality assessment of diagnostic accuracy studies checklist showed the papers were of good quality, a meta-analysis was not applicable because of the lack of eligible studies. In conclusion, CEUS seems to be promising in the detection of liver metastases; however, there have not been enough studies to conduct meta-analysis. Further studies are required before this promising method can be widely used.

Economic assessment of contrast-enhanced ultrasonography for evaluation of focal liver lesions: a multicentre Italian experience

BACKGROUND

The aim of this study was to evaluate the clinical and economic consequences of the introduction of contrast-enhanced ultrasonography (CEUS) into the diagnostic clinical algorithm for the characterization of incidental focal liver lesions (FLLs).

METHODS

This prospective study enrolled 485 subjects at three hospitals in Italy. Two diagnostic algorithms were utilized: (1) a classic patient work-up, which included baseline US followed by a CT or MR examination, and (2) a new patient management scheme in which, following the baseline US, a CEUS examination was performed. For each pathway, both direct and indirect health costs for the National Health System (NHS) at two of the three hospitals involved in the study were calculated. Clinical outcome was measured in terms of number of cases correctly diagnosed, using contrast-enhanced CT/contrast-enhanced MR as the reference standard.

RESULTS

CEUS correctly differentiated (benign vs. malignant) 559 of 575 lesions (97.2%), with a sensitivity of 98.1% and a specificity of 95.7%. Histological characterization was correct in 502 of 575 lesions (87%) with a sensitivity of 90.5% and a specificity of 85.4%. In terms of cost, the conventional diagnostic algorithm incurred for the NHS a total cost of Euro 134.576,60 vs. Euro 55.674,30 with CEUS, for a saving of Euro 78.902 (Euro 162 per patient). For the hospitals, the total cost was Euro 147.045 without CEUS vs Euro 61.979 with CEUS, for a saving of Euro 85.065,96 or Euro 175,39 per patient.

CONCLUSION

The routine use of CEUS for the characterization of FLLs provides significant cost savings, both for the NHS and for the hospital.

Characterization of hypoechoic focal hepatic lesions in patients with fatty liver: diagnostic performance and confidence of contrast-enhanced ultrasound

The objective of this study was to assess the diagnostic performance of contrast-enhanced ultrasound (CEUS) to characterize hypoechoic focal hepatic lesions (HFHL) in fatty liver (FL). A study group of 105 patients with FL and 105 HFHLs (52 malignant and 53 benign) underwent CEUS after SonoVue administration. Two blinded readers independently reviewed baseline ultrasound (US) and CEUS scans and classified each lesion as malignant or benign on a five-point scale of confidence, and recorded whether further imaging work-up was needed. Sensitivity, specificity, areas under the receiver operating characteristic (ROC) curve (A (z)), and interobserver agreement were calculated. We observed that the diagnostic confidence improved after reviewing CEUS scans for both readers (A (z)=0.706 and 0.999 and A (z)=0.665 and 0.990 at baseline US and CEUS, respectively; p<0.0001). Inter-reader agreement increased (weighted k=0.748 at baseline US vs. 0.882 at CEUS). For both readers, after CEUS, the occurrence of correctly characterized lesions increased (from 27/105 [27.5%] to 94/105 [89.5%], and from 19/105 [18.1%] to 93/105 [88.6%], respectively; p<0.0001) and the need for further imaging decreased (from 93/105 [88.6%] to 26/105 [24.8%], and from 96/105 [91.4%] to 40/105 [38.1%], respectively; p<0.0001). We conclude that CEUS improves the diagnostic performance of radiologists in the characterization of HFHLs in FL and reduces the need for further imaging work-up.

Characterization of focal liver lesions using contrast-enhanced sonography with a low mechanical index mode and a sulfur hexafluoride-filled microbubble contrast agent

PURPOSE

To characterize focal liver lesions (FLLs) using real-time contrast-enhancedsonography (CEUS) with a low mechanical index mode and a sulfur hexafluoride-filled microbubble contrast agent.

METHODS

CEUS was performed in 190 patients with FLLs, including hepatocellular carcinoma (HCC) (n = 107), liver metastasis (n = 21), intrahepatic cholangiocarcinoma (ICC) (n = 7), liver hemangioma (n = 37), focal nodular hyperplasia (FNH) (n = 11), regenerative nodule (n = 6) and liver lipoma (n = 1). The cadence contrast pulse sequencing technique and the contrast agent SonoVue(R) were used for CEUS examination. The enhancement patterns during the arterial, portal, and late phases were evaluated.

RESULTS

HCC showed hyperenhancement in 100 (93.5%) of 107 nodules during the arterial phase and hypoenhancement in 102 (95.3%) during the late phase. Liver metastases showed homogeneous enhancement in 8 of 21 (38.1%) nodules and a peripheral regular rim-like enhancement in 11 of 21 (52.4%) nodules during the arterial phase and marked hypoenhancement in 16 of 21 (76.2%) nodules during the late phase. ICC exhibited irregular rim-like enhancement in 4 of 7 (57.1%) nodules during the arterial phase and hypo-enhancement in 7 of 7 (100%) nodules during the late phase. Hemangioma showed peripheral nodular hyperenhancement, and progressive centripetal enhancement was seen in 35 of 37 (94.6%) lesions during the arterial phase. All 11 cases of FNH exhibited homogeneous hyperenhancement during the arterial phase and hyperenhancement (n = 1) or isoenhancement (n = 9) during the late phase. The sensitivity, specificity, and positive predictive value, respectively, were 88.8%, 89.2%, and 91.3% for HCC; 81%, 100%, and 100% for liver metastasis; 57.1%, 100%, and 100% for ICC; 94.6%, 100%, and 100% for liver hemangioma; and 90.9%, 97.8%, and 71.4% for FNH.

CONCLUSIONS

Low-mechanical index CEUS permits real-time, complete assessment of vascularity in FLLs, which in turn facilitates their characterization.

Focal liver lesions: sinusoidal phase of CEUS

Ultrasound examination is the first imaging modality for hepatic study in neoplastic and chronic liver diseases. Focal liver lesions frequently cause diagnostic problems in terms of characterization, especially when small and hypoechoic to the rest of the parenchyma. Contrast--enhanced ultrasonography (CEUS) has shown its value in the characterization of focal liver lesions. This study assessed the value of the sinusoidal phase of CEUS with a second-generation contrast agent in the characterization of focal liver lesions to distinguish benign from malignant. Two hundred hepatic lesions with suspicious features at baseline ultrasound were prospectively studied with CEUS. Sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy of the sinusoidal phase in the characterization of benign versus malignant liver lesions were evaluated. Hypoechogenicity of the focal liver lesion, during the sinusoidal phase of CEUS, allowed the diagnosis of malignancy with a sensitivity of 85%, specificity of 88%, positive predictive value of 92%, negative predictive value of 77%, and diagnostic accuracy of 86%. The diagnostic confidence in the diagnosis of malignancy significantly increased, with receiver operating characteristic curve areas from 0.536 for baseline ultrasound to 0.902 for the sinusoidal phase of CEUS.

Imaging of focal liver lesions: low-mechanical-index real-time ultrasonography with SonoVue

OBJECTIVE

The purpose of this study was to evaluate the usefulness of a contrast-enhanced contrast-specific ultrasonographic technique with a low mechanical index for characterization of focal liver lesions.

METHODS

Contrast-specific ultrasonography was used to assess 144 patients with 147 focal liver lesions: 87 primary liver carcinomas, 27 hemangiomas, 16 focal nodular hyperplasias, 5 hepatic abscesses, 3 inflammatory pseudotumors of the liver, and 9 metastases. A sulfur hexafluoride gas-based contrast agent was used with a mechanical index of 0.08 to 0.11.

RESULTS

On contrast-enhanced ultrasonography, the typical hemodynamic pattern of primary liver carcinoma was the whole-lesion enhancement or mosaic enhancement in the arterial phase with an enhancement defect in the late phase (sensitivity, 92.0%; specificity, 86.7%). The most common enhancement pattern of hemangioma was that enhancement appeared in the periphery first and progressively filled into the lesion center (sensitivity, 96.3%; specificity, 97.5%). The enhancement pattern of focal nodular hyperplasia was that the whole lesion enhanced early and rapidly in the arterial phase with a centrifugal radiating configuration and appeared isoechoic or hyperechoic until the late phase (sensitivity, 87.6%; specificity, 94.5%). The central scar was detected in 31.3% of cases in the late phase. The specific enhancement of a hepatic abscess was the honeycomblike enhancement in all phases (sensitivity, 80.0%; specificity, 100%). No enhancement of a lesion in all phases was specific for an inflammatory pseudotumor of the liver.

CONCLUSIONS

Contrast-enhanced real-time ultrasonography is a promising approach in the noninvasive characterization of focal liver lesions and can be useful as a first-line imaging technique clinically when a focal liver lesion is detectable on ultrasonography.

Benign focal liver lesions: spectrum of findings on SonoVue-enhanced pulse-inversion ultrasonography

The prevalence of benign focal liver lesions (BFLL) is high both in the general population and in patients with known malignancies. The gray-scale ultrasound (US) technique is usually the first-line imaging modality used in the radiological workup of such lesions, but unfortunately it lacks specificity. Furthermore, Doppler examination may often be unsatisfactory owing to motion artefacts, or when small or deeply located lesions are evaluated. Recently, microbubble-based contrast agents used in combination with gray-scale US techniques, which are very sensitive to nonlinear behavior of microbubbles, have led to a better depiction of both microvasculature and macrovasculature of focal hepatic masses, thus improving the reliability of using US in the assessment of liver tumors. This review illustrates the spectrum of enhancement patterns of BFLL on contrast-enhanced ultrasonography with SonoVue, a second-generation microbubble-based contrast agent.

Liver haemangiomas undetermined at grey-scale ultrasound: contrast-enhancement patterns with SonoVue and pulse-inversion US

The objective of this study was to describe the spectrum of contrast-enhancement patterns of hepatic haemangiomas undetermined at grey-scale ultrasound (US) on SonoVue-enhanced pulse-inversion (PI) US. Twenty patients (11 women, nine men) with 35 haemangiomas (size range: 1-7 cm; mean: 3.1 cm) undetermined at baseline US underwent PI at low M.I. (0.05-0.08) after i.v. injection of SonoVue. All haemangiomas were confirmed by typical helical computed tomography (CT) and/or magnetic resonance imaging (MRI) findings. US examinations were videotaped and then reviewed by two experienced radiologists blinded to the final diagnosis. Readers evaluated by consensus the baseline echogenicity and the dynamic enhancement pattern of each lesion, in comparison with adjacent liver parenchyma. After administration of SonoVue, 31/35 (88%) haemangiomas showed peripheral hyperechoic nodules in the arterial phase, followed by progressive centripetal fill-in, which was complete in 25/35 cases and incomplete in 6/35 cases. Three out of 35 (9%) haemangiomas showed rapid and complete fill-in in the arterial phase, which persisted in the portal and delayed phases. Finally, 1/35 haemangiomas (3%) showed a rim of arterial contrast enhancement with progressive and complete centripetal fill-in in portal-venous and delayed phases. In conclusion, PI after the administration of SonoVue enabled the depiction of typical contrast-enhancement patterns in haemangiomas undetermined at baseline US.